This invention relates to a transparent electrical discharge machining fluid and more particularly it relates to a machining fluid which is used for electrical machining called as electrical discharge system such as electrical discharge machining, wire cut electrical discharge machining, etc. and which requires less measures for flame prevention even when it is used in a large amount because of its low flexibility, is superior in characteristics as a machining fluid because of less increase in viscosity and less decrease in specific electric resistance and has superior operability because of excellent transparency.
Hitherto, hydrocarbon oils high in insulation have been used as machining fluid for electrical machining.
However, conventional hydrocarbon oils have the defect of reduction in production efficiency because of decrease in machining speed due to cutting dust-like material produced at machining and carbon liberated from the hydrocarbon oils. There are further problems that when applied voltage is increased because of reduction of specific electric resistance, the machined surface becomes rough and exhaustion of electrode is hastened.
Furthermore, hydrocarbon oils are generally high in flash point and so sufficient preventive measures for flaming must be adopted at use and especially when they are used in a large amount, considerable costs and labors are required for adoption of the measures. As electrical machining fluids free from the problems in the conventional hydrocarbon oils, there have been proposed various machining fluids such as emulsion type electrical machining solutions comprising an oil of high electrical resistance to which water is added. (cf. Japanese Patent Unexamined Publication (kokai) Nos. 6416/80 and 181552/83).
However, when said electrical machining fluids are W/O emulsions, specific electric resistance reaches nearly 0 and discharge machining becomes difficult and when machining is forcibly made, applied voltage must be increased, resulting in further acceleration of shortening of life of electrode due to increase in load applied to the electrode. Furthermore, since they are emulsions, their flash point is low and there are much possibilities of flaming. Besides, they are high in viscosity and removal of cutting dust-like material and carbon particles which get mixed in during machining is difficult. Moreover, in the W/O type emulsion, water is continuous phase and electrical discharge machining is impossible, though electrolytic machining is possible.